Synthesis and Physicochemical Characterization of Pure Diammonium Phosphate from Industrial Fertilizer M. Gargouri, C. Chtara, P. Charrock, Ange Nzihou, H. El Feki
To cite this version:
M. Gargouri, C. Chtara, P. Charrock, Ange Nzihou, H. El Feki. Synthesis and Physicochemical Characterization of Pure Diammonium Phosphate from Industrial Fertilizer. Industrial and engineer- ing chemistry research, American Chemical Society, 2011, 50 (11), p.6580-6584. 10.1021/ie102237n. hal-01634018
HAL Id: hal-01634018 https://hal.archives-ouvertes.fr/hal-01634018 Submitted on 7 Mar 2019
HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Synthesis and Physicochemical Characterization of Pure Diammonium Phosphate from Industrial Fertilizer M. Gargouri,*,† C. Chtara,‡ P. Charrock,§ A. Nzihou,^ and H. El Feki† †Laboratory of Materials Sciences and Environment, Science University of Sfax, 3010 Sfax, University of Sfax, Tunisia. ‡Chemical Group of Tunisia, Gabes §LERISM, IUT P.Sabatier, Castres 81104, France ^ RAPSODEE, Ecole des Mines d0Albi-Carmaux, campus Jarlard, 81013, Albi, France
ABSTRACT: Diammonium phosphate (DAP) is produced from industrial phosphoric acid that contains large amounts of anionic and cationic impurities (Co, Cu, Fe, Mn, Mo, Ni, Zn, F, As, Al, Hg, Pb and Cd). Consequently all those impurities will be found in DAP. However, the industrial DAP obtained can be used as fertilizers, but cannot be used for some industrial application like pharmaceutics and cosmetics. After purification, the price of DAP is three times more expensive than the same product before purification. The procedure for purification of industrial DAP is a recrystallization, by using several mixtures of solvents. The physicochemical characterization of this fertilizer upstream and downstream from the purification, through spectroscopic analyses and chemical analyses, shows that recrystallization eliminates impurities. Purified DAP was obtained, the physicochemical properties of which are comparable to those of the pure commercial DAP (Fisher).
1. INTRODUCTION Diammonium phosphate (DAP) is an important commercial fertilizer. The important water-soluble P fertilizers include mono- ammonium phosphate (MAP) and diammonium phosphate (DAP).1 The fertilizer is produced industrially in large quantities via the reaction between gaseous ammonia and green phosphoric acid. The reaction is exothermic; the equation for the neutralization reaction between ammonia and phosphoric acid is as follows:2
2NH H PO f NH HPO 3 þ 3 4 ð 4Þ2 4 When the molar ratio (MR) of ammonia to phosphoric acid is 2, DAP is formed.2 The phosphoric acid used in producing DAP fi can be crude unpuri ed acid obtained by dissolving phosphate Figure 1. Curve solubility of recrystallized DAP. rock with sulfuric acid. In this case, crude DAP results, which may be adequate for some applications. However phosphate rock may followed by reacting ammonia with the resulting extract to obtain contain heavy metals and these can be transferred to the fertilizer, diammonium phosphate containing a small amount of impurities. and further to crops. fi However, this extraction process cannot be regarded as an Two options are available to produce puri ed DAP: (1) use industrially advantageous process owing to its complicated steps.3 purified phosphoric acid; (2) purify the DAP. For producing fi fi Our work began with the puri cation of monoammonium industrial puri ed diammonium phosphate from wet process phosphate (MAP) from industrial fertilizer, and the results are phosphoric acid, it is necessary to purify the phosphoric acid in very encouraging.4 This prompted us to pursue this study on advance according to a process of extracting phosphoric acid another product of the same family, DAP. from wet process phosphoric acid according to a solvent process, In the present work, we are interested in eliminating impurities from industrial DAP. We present here the physicochemical characterization of DAP fertilizer upstream and downstream of Table 1. Chemical Compositions of the DAP Upstream and fi Downstream from the Recrystallization the puri cation process, with an aim to determine the performance
P2O5 N H2O MR samples (wt) % (wt)% (wt) % (N/P) pH
plant DAP 46.05 17.65 1.50 1.94 7.6 plant DAP recrystallized 49 18 1.68 1.86 7.9 Table 2. Determination the Impurity Present in the DAP Upstream and Downstream from the Recrystallizationa
sample (ppm) Fe Al Mg Ag As Co Pb Hg Si Sn Ti Cr Zn Cd Cu Ni Mn V
plant DAP 6769 4273 4907 6 26 5419 22 3 150 382 93 525 1203 34 59 25 65 1341 plant DAP recrystallized (water-alcohol) 24 37 14 - 3 3 7 - 70 - 2 27 41 3 4 17 1 47 commercial DAP (Fisher) 15 22 9 - 3 2 7 - 38 - - 25 11 3 2 17 - 9 a Dash (-) = trace.
Figure 2. The analysis by means of IR of the industrial DAP upstream from the recrystallization.
Figure 3. The analysis by means of IR of the industrial DAP downstream from the recrystallization and pure commercial DAP (Fisher). of recrystallization. We also compare the recrystallized DAP to the between 273 and 400 K and at 400 rpm stirring rate. The suspension commercial DAP (Fisher). was dissolved in mixed solvent (70% water 30% alcohol). After À that we add a quantity of charcoal in the solution. The suspension 2. EXPERIMENTAL SECTION was filtered, and the solution was cooled to 273 K, whereupon crystals appeared. We recrystallized the DAP using a mixture of 2.1. Recrystallization. Crystallization experiments of DAP solvent, water, and alcohol. Impurities were analyzed by inductively (fertilizer synthesized in industry from Tunisia) were carried coupled plasma-optical emission spectroscopy (ICPOES). Figure 4. The analysis by MEB of the industrial DAP upstream and downstream from the recrystallization.
Table 3. The Wavelength of the Vibration Mode of DAP KappaCCD Server Software (Nonius, 2004); program(s) used Upstream (ur) and Downstream (dr) from the Recrystalliza- to solve structure are SHELXS97. The spectra of X-ray powder tion and Pure Commercial DAP (Fisher) diffraction (XRPD) is determined by a Seifert 3000. T.T. spectrometer. band limit of pure commercial 1 8,9 bands absorption (cmÀ ) DAP (ur) DAP (dr) DAP (Fisher)
PO 3- υ : 1000 800 954 886 893 3. RESULTS AND DISCUSSION 4 1 À υ : 500 300 531 454 451 The principal chemical compositions of the DAP upstream 2 À υ3: 1200 1000 1097 1076 1077 and downstream from the recrystallization are presented in À Table 1. After purification, the % P O and % N were increased υ4: 650 500 618 553 553 2 5 À while keeping the molar ratio (MR) range between 1.8 and 2.0. Also, after purification the percentage of H O and value of pH are NH ∂ : 1600 1575 1516 1516 1516 2 3 a À slightly changed but in the various ranges stated. There is 25% of ∂ : 1500 1300 1400 1403 1402 s À impurities by weight in the crude industrial DAP. Diammonium phosphate granules contain various com- NH þ υ : 3300 3030 3119 3119 3099 4 NH À pounds (Ca, Mg)(NH4)(Fe, Al)(PO4)(F, OH)H2O that are insoluble in water and can comprise up to 10% of the total P H O υ : 3600 3100 3119 3119 3099 7 2 OH À content of fertilizers. The DAP contains toxic elements such as (Cd, Zn, Cu, and Ni) which are toxic for plants and have the ff 2.2. Analytical and Testing Methods. P2O5 content in the potential for adverse e ects on human health due to the transfer solution is determined gravimetrically. The molar rapport of of metals from soils to food corps. Thus, it is important to ammonia to phosphoric acid (MR) was obtained by titration eliminate or reduce these toxic elements in DAP. The analysis of with standard 0.5 M NaOH and 0.5 M HCl solutions. The the DAP after purification is given in Table 2 and shows that the amount of HCl and NaOH added was used to calculate the MR quantity of impurity decreases. The results are comparable to that is equal to 2 (volume of NaOH/volume of HCl), according those of the commercial DAP (Fisher). to the method described in ref 5. A pH Meter was employed to After recrystallization, the melting point was found to be measure the pH values of slurries. N content in the solutions was 194 °C, close to the one of laboratory grade DAP (196 °C). determined by the Kejdahl method. Melting points were deter- The curve solubility of recrystallized DAP, that was deter- mined with a METTLER FP62 that uses a capillary tube. The mined following a standard procedure described by Mullin,6 is curve solubility was determined following a standard procedure shown in Figure1. The solubility of a solute is most conveniently described by Mullin.6 IR spectra were determined by a FTIR stated as the parts by weight per part (or 100 parts) by weight of system spectrum BX Perkin-Elmer spectrometer. The analysis by solvent. scanning electron microscope (SEM) is determined with a MEB The analysis by means of IR of the DAP before and after Philips serie XL 30. Data collection is realized by using recrystallization is presented in Figures 2 and 3. Table 4. Crystal Data Details and Structure Refinement of the Plant DAP Downstream from the Recrystallization and Commercially Pure DAP
DAP pure commercial recrystallized DAP (Fisher)
I. Crystal Data
formula (NH4)2HPO4 (NH4)2HPO4 formula weight (g/mol) 132.06 132.06 system monoclinic monoclinic space group P21/cP21/c a (Å) 10.781(2) 10.729(5) b (Å) 6.771(2) 6.682(5) c (Å) 8.047(2) 8.009(5) 0 109.72(2) 109.670(5) V (Å3) 448.1 (2) 540.7(6) Z 44 3 Fcal (g cmÀ ) 1.600 1.622 Figure 5. The analysis by XRPD of the industrial DAP. F (000) 280 332 1 μ (Mo KR) (mmÀ ) 0.427 0.433 crystal color colorless colorless II. Intensity Measurements temperature (K) 293 (2) 293 (2) wavelength Mo KR (Å) 0.71073 0.71073 measurement area: h 13 < h < 13 12< h < 12 À À k 1
The characteristic wavelengths of the vibration modes of DAP are illustrated in Table 3, which shows the presence of the four 3- modes of vibrations ascribed to PO4 observed at about 444, 1 539, 917, and 1110 cmÀ , the vibrations of ammonia observed 1 about 1400 cmÀ , and a wide band attributed to H2O and NH4þ 1 stretching modes observed around 3137 cmÀ . In addition, the analysis by sweeping electron microscope (MEB) of the industrial DAP after recrystallization, showed that the elements of aluminum, magnesium, and copper are elimi- nated, and the quantity of sulfur was decreased (Figure 4). The crystal structure of the recrystallized diammonium phos- phate (NH4)2HPO4 has been determined by X-ray single crystal analysis at room temperature. The space group is P21/c10 with lattice parameter a = 10.781(2) Å, b = 6.771(2) Å, c = 8.047(2) Å, fi and Z = 4. The re nement converged to R1 = 0.0231 and RW2 = 0.0660. The analysis by X-ray diffraction showed that the purification of the DAP did not change the crystalline system (monoclinic). Crystal data details and structure refinement are given in Table 4 and show that the crystallographic parameters of Figure 7. The analysis by XRPD of the pure commercial DAP (Fisher). recrystallized DAP are close to the pure DAP (Fisher), which (8) Nakamoto, K. Infrared and Raman Spectra of Inorganic and justifies the performance of the recrystallization. Coordination Compounds; Wiley: New York, 1984. In addition, the analysis by X-ray powder of industrial DAP (9) Parker, F. S. Application of IR Spectroscopy in Biochemistry, Biology downstream of the purification (Figure 6) shows an elimination and Medicine; Hilger, A., Ed.; Plenum Press: New York, 1971. of the impurities that were found upstream of the purification (10) Khan, A. A.; Roux, J. P.; James, W. J. The crystal structure of (Figure 5), and we got a good crystalline product that resembles diammonium phosphate, (NH4)2HPO4. Acta Crystallogr., Sect. B 1972, 28, 2065–2069. the pure commercial DAP (Fisher) (Figure 7).
4. CONCLUSION The long-continued application of impure DAP can redis- tribute and elevate heavy metal concentrations in soils. The redistribution of heavy metals can adversely affect water re- sources and endanger the health of surrounding ecosystems and human populations. Thus, it is important to eliminate the different toxic elements present in the fertilizer in order to prevent transfer to plants and humans, in this case with the use of purified fertilizers in biological agriculture. On the other hand, you can also use the purified product in the pharmaceutics and cosmetic industries. fi After puri cation, the % P2O5 and % N increased, while the molar ratio (MR) remained between 1.8 and 2.00 and the products obtained contained 1.5 2% H2O and had a pH value of 7 8. The analysis by X-rayÀ diffraction showed that the purifica- tionÀ of the plant DAP did not change the crystalline system (monoclinic). The physicochemical characterization of the industrial DAP downstream of the purification, through spectroscopic analyses and chemical analyses, showed that we obtained purified DAP whose physicochemical properties are comparable with those of the pure commercial DAP (Fisher).
’ AUTHOR INFORMATION Corresponding Author *E-mail: [email protected].
’ ACKNOWLEDGMENT The authors thank Dr. A. Driss from the University of Tunis, Tunisia, for his valuable collaboration.
’ REFERENCES (1) Duraisamy, V. P. Role of inorganic and organic soil amendments. Aust. J. Soil Res. 2005. (2) Campbell, G. R.; Leong, Y. K.; Berndt, C. C.; Liow, J. L. Ammonium phosphate slurry rheology and particle properties The influence of Fe(III) and Al(III) impurities, solid concentration, and degree of neutralization. Ind. Eng. Chem. Res. 2006, 61, 5856–5866. (3) Akiyama, A. Studies on chemical fertilizers. K.K. Nissin Syuppan 1976. (4) Gargouri, M.; Chtara, C.; Charock, P.; Nzihou, A.; Elfeki, H. Synthesis and physicochemical characterization of pure monoammo- nium phosphate (MAP) from industrial fertilizer. J. Chem. Chem. Eng. 2010, 49,. (5) Shengwei, Tang; Hui, Guo; Jiankang, ying; Bin., Liang Physi- colchemical propreties of acidic ammonium phosphate slurries. Ind. Eng. Chem. Res. 2004, 43, 3199. (6) Mullin, J. Crystallization; Butterworth-Heinemann : Oxford, GB, 2001. (7) Gilkes, R. J.; Mangano, P. Poorly soluble iron-aluminium phos- phates in ammonium phosphate fertilizers: Their nature and availability to plants. Aust. J. Soil Res. 1983, 21, 183–194.